Purpose/background: Development of the Digit Symbol Substitution Test (DSST) was initiated over a century ago as an experimental tool to understand human associative learning. Its clinical utility, owing to its brevity and high discriminant validity, was first recognized in the 1940s, and now the DSST is among the most commonly used tests in clinical neuropsychology.
Methods: Specific studies and articles were reviewed to illustrate what the test measures, to evaluate its sensitivity to change, and to discuss its use in clinical practice.
Results: The DSST is a valid and sensitive measure of cognitive dysfunction impacted by many domains. Performance on the DSST correlates with real-world functional outcomes (eg, the ability to accomplish everyday tasks) and recovery from functional disability in a range of psychiatric conditions including schizophrenia and major depressive disorder. Importantly, the DSST has been demonstrated to be sensitive to changes in cognitive functioning in patients with major depressive disorder and offers promise as a clinical decision-making tool for monitoring treatment effects in this and other disorders affecting cognition.
Implications/conclusions: The DSST is sensitive to the presence of cognitive dysfunction as well as to change in cognitive function across a wide range of clinical populations but has low specificity to determine exactly which cognitive domain has been affected. However, the DSST offers a practical and effective method to monitor cognitive functions over time in clinical practice.